The invention relates to an internal shaping tool for deforming a metal sheet or strip into a pipe. The tool has at least two rollers that are pivotable about swivel axes and that start on one side of the metal sheet for shaping same.
In pipe manufacturing, according to one common technology first a flat metal strip, generally wound from a coil, is shaped into a tubular element and in a subsequent operation is welded at the joint that is formed on the edges of the strip. For the shaping of the metal strip into the tubular element, devices are known in practice that have the above-described internal shaping tools, typically acting with outer tools that engage the outer face of the strip to press its inner face against the internal tool.
The known internal shaping tools employ rollers that are either fixedly or rigidly provided in a defined position on a hearing element, or are each positioned in a pivotal holder.
The shape of the body to be manufactured depends on the final dimensions to be achieved, as well as the material properties of the metal strip, i.e. its tensile strength, yield point, and also its thickness. For the known internal shaping tool having fixed rollers, response to a change in characteristics for the pipe or shaped body to be shaped can be made only with great effort. In particular, a modification using a different or rebuilt internal shaping tool is necessary.
However, for the known rollers that are pivotal via their holders it is also not possible to achieve a desired configuration of the pipe geometry via adjustment of their angular positions. Namely, the pivot point is arbitrarily selected and has no relation to the shape to be produced, and thus also cannot be compensated for by the contoured shape of the rollers.
In practice, therefore, it has been shown that due to the inadequate adaptability of the internal shaping tool the rollers often do not bear on the workpiece over their full width, resulting these roller running on their edges. This results in surface damage to the metal strip being shaped.